1. Field of the Invention
The present invention relates to air tools equipped with an air motor and, more particularly, to rotationally driven air tools such as an air grinder using a rotational driving force from a rotational output shaft of an air motor.
2. Description of the Related Art
In general, an air grinder has a structure in which a rotation transmitting shaft is drivably connected to a rotational drive output shaft of an air motor through bevel gears, and a rotary abrasive disc is attached to the distal end of the rotation transmitting shaft (for example, Patent Literature 1).
Patent Literature 1: Japanese Patent Application Publication No. 2007-98539
In power transmission using gears, lubricant such as grease is supplied to mutually meshed gears. In rotationally driven air tools, e.g., the above-described air grinder, lubricant undesirably scatters to the surroundings as the gears rotate because of a high rotational drive speed of the rotationally driven air tool. Therefore, the gears need to be replenished with lubricant every predetermined time period. It is, however, desirable to minimize the frequency of such lubricant replenishment. An object of the present invention is to provide a rotationally driven air tool capable of retaining a lubricant in a gear for a long period of time, in view of the above-described circumstances.